Today’s personal computers are powerful but,
most of the time, a large proportion of their
computational power is left unused. A desktop
grid takes this unused capacity, no matter what
its location, and puts it to work solving scientific
problems. With over 1 billion desktop computers
in use, desktop grids can offer a low cost, readily
available computing resource for scientists while
allowing citizens across the world to contribute
to scientific research. Together with grids and
supercomputers, desktop grids can be a useful
complement to the e-Infrastructure landscape.

Desktop grids fall into two categories - local and volunteer.
While local desktop grids are comprised mainly of a set
of computers at one location, a business or institute for
example, the resources in a volunteer desktop grid are
provided by citizens all over the world.

Today researchers are using desktop grids to simulate
protein folding (Folding@home), find ways to provide
clean water (IBM’s World Community Grid), and model
climate change (Climateprediction.net). Scientific problems
that can be split up into small tasks and sent to different
computers for computation are perfect for solving with
desktop grids. These projects farm out tasks to computers
located across the globe which send the results back to
scientists once they are complete.

Desktop grids can open up computing to researchers that
otherwise would be unable to access such large amounts
of computing power. For example the Citizen Cyberscience Centre has been set up to help scientists in developing
countries access the power of internet-based volunteer
networks. Initiatives such as Africa@Home and Asia@Home have also encouraged more researchers in these
regions to use desktop grids.

A large majority of volunteer computing projects are
based on open source software called BOINC. BOINC
allows scientists to plug their own projects into the
software, so volunteers can easily download and run
applications on their computer. The BOINC client,
used by the volunteers, can be configured to run only
when the PC is not in use, often as a screensaver, or
to run at the lowest priority while the PC is in use.
Other desktop grid middlewares include XtremWeb,
developed by INRIA/CNRS, which is mainly used to
manage computations on desktop computers within
an organisation.

David Anderson, BOINC director - “BOINC
is being used by over 50 volunteer computing
projects, doing research in everything from
quantum mechanics to cosmology. About
430,000 PCs from all over the world, many
of them equipped with GPUs, participate in
these projects. Together they supply about
6 PetaFLOPS of computing power.”

LHC@home 2.0 aims to bring the world’s largest particle
accelerator into your home. The platform – an extension
of the already successful LHC@home – allows volunteers
to connect to CERN-based research projects simply
by donating their extra computing power. The project
Test4Theory, for example, simulates high-energy particle
collisions which scientists can compare to real-life collisions,
such as those occurring in the Large Hadron Collider (LHC).

“My dream is to be able to establish a ‘virtual LHC’,
which would require being able to generate 40 million
events per second, as much as the real LHC, running
at full steam,“ says Peter Skands, the lead scientist
behind Test4Theory. “We estimate that it would take
somewhere between 10 000 and 100 000 connected
computers to achieve this, a combined amount of
computing power that we have only faintly begun to
imagine, since we started working with LHC@home 2.0.
With the enthusiasm we have seen in the public so far,
there definitely appears to be awesome possibilities for
what we can do with this platform.“

Nicole Vasapolli, BOINC volunteer - “I’m
a meteorologist so was originally interested
in donating my computing time for climate
research as it was related to my work. But, as
time went on, I began to take part in many other
exciting life science projects, to assist scientists
in solving pressing problems. I’ve found that
BOINC is free, easy to install and it’s an entertaining way to be
part of scientific progress."

Anyone going on holiday to a malaria-affected country
will often head to their doctor for a course of malaria
tablets. But for those who live in countries at risk,
taking preventative medicines is impractical.

So what do citizens of these areas do? They use
mosquito nets or insect repellent, treat their houses
with insecticide, or get rapid treatment in the event of
becoming ill.

While none of these methods are perfect, each can
make a big impact given the widespread nature of the
disease. Malaria is preventable and treatable but three
quarters of a million people die from it every year,
putting healthcare services in affected countries under
enormous strain.

Healthcare providers and governments need to find
ways to determine the most effective combination of
treatments for their area. They can use mathematical
models to simulate the effectiveness of different
combinations of malaria control, and work out what
the best solution is for a given situation.

In 2003 researchers at the Swiss Tropical and Public
Health Institute started running malaria models to
answer these questions. Starting with just 50 of their
own PCs, they soon opened up the project via BOINC
and malariacontrol.net was born. Today 50,000 people
contribute computing time to the project, through
over 70,000 PCs. In total, malariacontrol.net and its
volunteers have notched up over 10,000 CPU years
helping healthcare professionals fight malaria.

Desktop grids are just one of a number of ways in which
researchers can access computing capacity. They can
provide a useful complement to the other facilities in the
e-infrastructure landscape. While supercomputers are
able to solve a wide variety of complex computational
problems they are expensive and are limited to a relatively
small number of researchers. Cluster-based grids can
provide a cheaper solution for more researchers, but for a
more limited set of applications. Assuming the computers
making up a desktop grid are already paid for, they can
open up computational research to more scientists at an
even lower cost.

The EDGeS (Enabling Desktop Grids for e-Science)
project, which has now finished, worked to connect
desktop grids to the wider EGEE (Enabling Grids for
E-sciencE) European infrastructure. Using the g-Lite middleware the project defined common policies to
integrate desktop grids into existing EGEE service grids.
Today EDGI (the European Desktop Grid Initiative)
is continuing this work by connecting desktop grids
into the European Grid Infrastructure (EGI). As well as
focusing on gLite, EDGI aims to build bridges to the
UNICORE and ARC middlewares.

Desktop grids have high capacity but not a guaranteed
quality of service as the available computing power
depends on which computers are not being used. EDGI
hopes to include a cloud in the infrastructure, which can
be used as and when necessary. This will allow the service
to be used by applications which need to be completed
within a specific deadline.

By integrating desktop grids with other e-infrastructures,
researchers can run applications across different types of
computing resources, matching parts of the computational
problem to the most suitable execution environments. For
example, some parts of an application can be run on a
desktop grid, and others on a high-end supercomputer.
Collaborations between a number of infrastructure
providers, such as those established through the
International Desktop Grid Federation (IDGF) are already
in place to enable these applications. On the international
scale the DEGISCO project aims to export and share
desktop grid knowledge outside of the EU, while policy
bodies like e-IRG are preparing the setup of the legal and
political frameworks.

Mikhail Posypkin, Institute for Systems
Analysis of Russian Academy of Sciences - “Desktop grids offer a cost-effective
alternative to supercomputers or service grids.
Unlike supercomputers or service grids large
desktop grids are almost free: all you need is a
meaningful distributed application. Presently
desktop grids can contribute their resources to existing grid
infrastructures thus producing a really powerful combined
distributed computing infrastructure.”

Vicky Huang, ASGC - “Asia is a geographically
large region, with diverse and scattered
resources (technologies and facilities) coupled
with the general problem of insufficient
investment from government in academic
hardware supply. As such, the concept of
desktop grids and volunteer computing is very
suitable and useful to popularise in the Asia-Pacific region
through initiatives such as DEGISCO.”

Desktop grids can provide a variety of different benefits,
however their use raises a number of challenges. A Desktop Grids for eScience Road Map produced by the
DEGISCO project in July 2011 took a closer look at some
of the following issues:

• Supporting a desktop grid: Aside from having to
develop applications that can run across a number of
heterogeneous systems, the distributed nature of a
desktop grid poses unique problems. As volunteers provide
the resources, it is difficult to test and fix applications.

• Making it green: Desktop grids are often touted as a
‘green solution’ as they use computing resources already
in existence. However, in reality, determining whether a
desktop grid is green, or not, is complex. How volunteers
choose to donate their computing time plays a big part
in this – adding on a CPU load to a machine running
at a low capacity doesn’t cost much energy, but using
a computer that would otherwise be switched off does.
Even the country a machine is running in can make a real
difference. Connecting a computer in a hot country such
as Dubai to a desktop grid is likely to use more energy, as
the machine needs to be kept cool.

• Local policies: Desktop grids are subject to the local
ICT policies at the institute or organisation that is hosting
the donated computer. For example, if a company
chooses to switch off computers at night, this can affect
the availability of the desktop grid.

• Evolving hardware: Today increasing numbers
of people are accessing the internet through new
technologies such as mobile phones instead of PCs.
In the future this evolving situation could have
consequences for the desktop grid concept as it
currently stands.

Morgan Duarte, BOINC volunteer - “I’m
sharing my computing resources with BOINC
to help solve tomorrow’s challenges and
be more involved in scientific progress and
our future. I believe it is an efficient way to
use our continuously increasing computers’
power without affecting my own personal
use. For me, volunteering my computer for science is
very rewarding.”

Leslie Versweyveld, AlmereGrid & IDGF - “The special feature desktop grids have to
offer is that they are already part of the
e-Infrastructures landscape. We are actually
sitting on a huge source of computational
power that is largely left unused in
numbers of universities, research institutes,
companies, home offices and households. It is already there,
we only need to tap into it, technically gain access to it and
transform this enormous resource of computational power to
fuel e-science research in all possible areas. Basically, it is a
mere question of ecological recycling.”

When Einstein@Home discovered a new pulsar its
discovery wasn’t credited to astronomers, but to its
volunteers - Daniel Gebhardt, from Mainz, Germany,
and husband-and-wife team Chris and Helen Colvin
of Ames, Iowa.
Pulsars are highly magnetised, rotating neutron stars that
emit a beam of electromagnetic radiation. Einstein@Home,
a BOINC project, was originally set up to search for
gravitational waves in data from the US LIGO Observatory.

However in March 2009, the project also began to
use its volunteers’ computers to search for signals
from radio pulsars in observations from the Arecibo
Observatory in Puerto Rico.
The new pulsar, discovered in October 2010 and named
PSR J2007+2722, was the first deep-space discovery by
Einstein@Home. Since then a further seven pulsars have
been discovered by Einstein@Home volunteers, showing
how donating your computer can make a real difference.

Francois Grey, Citizen Cyberscience Centre - “In my view, the most revolutionary aspect of
volunteer computing is the public participation.
Far from being passive, many participants turn
volunteer computing into a serious hobby. Some
contribute to debugging the software, others
help newcomers in the forums, still others set
up teams and events to encourage more participation. I predict
that ultimately, this will lead to public involvement in setting the
agenda for the research that is carried out using public resources.
Just as has already happened for journalism on the web, the
distinction between amateur and professional will start to blur.”

Unlike supercomputers or cluster-based grids, desktop
grids have an extra component that needs to be managed
– their volunteers. Using volunteers to donate computing
time forms the basis of all volunteer desktop grids, and can
create positive links between citizens and science.

The first step - recruiting volunteers - needn’t be a
difficult one. When the project LHC@home began, its
creators thought it would attract no interest. However
one thousand people downloaded the application in
the first 24 hours with no publicity effort at all. Often
volunteers are interested in the area of science they are
contributing towards such as searching for new drugs
or ways to generate clean water. AlmereGrid has taken
recruitment one step further, by setting up a ‘city grid’
intended to reach out to volunteers that may not be
traditionally interested in donating computing time.
AlmereGrid has partnered with local and national
companies across Almere in the Netherlands to
disseminate information on volunteer computing and
get more people interested in the topic.

While projects do not need to pay volunteers to use
computing resources, they do need to keep volunteers
informed. To ensure volunteers’ interest is sustained
over a project’s lifetime they should be provided with
feedback and information on how the project’s research
is progressing.

The Charity Engine has ambitions to be a worldwide
computer. Launching in summer 2011, Charity Engine
will provide volunteers’ computing time to a collection
of hand-chosen projects and raise money for charities
at the same time. By joining Charity Engine, its
volunteers will also have the chance to win a cash prize
of up to a million d ollars, every few weeks.

Charity Engine raises funds for its associated charities,
as well for its prize draws, by selling volunteers’
computing time in bulk to science and industry. Its
volunteers are not asked to support any particular
science project they simply agree to let Charity Engine
send ethical work to their PCs.

“Our volunteers are joining to make computergenerated
charity donations and prize draw entries,
they might not actually care about the science,“ says
Mark McAndrew, founder of Charity Engine. “But that’s
fine, because all that idle, wasted computing power
will make Charity Engine the ultimate supercomputer -
and we love the science.“

CPU: Central Processing Unit; a microprocessor (a
processor on an integrated circuit) inside a computer
that can execute computer programs.

GPU: Graphics Processing Unit; a device that renders
graphics for a computer. GPUs have a highly parallel
structure that makes them more
effective than generalpurpose
CPUs for some complex processing tasks.

Quality of service: the ability to guarantee a certain
level of performance.